JP4400768B2 - Solution casting method - Google Patents

Description

【００４９】
劣化防止剤の添加量は、０．００１〜５％が好ましく、０．０１〜１％がより好ましい。添加量が０．００１％未満であると添加効果が少なく、添加量が５％を超えると、原料コストが上昇して不利である。
【００５０】
前記微粒子粉体としては、シリカ、カオリン、タルク、ケイソウ土、石英、炭酸カルシウム、硫酸バリウム、酸化チタン、アルミナなどを目的に応じ、任意に用いることができる。これら微粒子粉体はポリマー溶液に添加する前に、高速ミキサー、ボールミル、アトライター、超音波分散機等、任意の手段でバインダー溶液中に分散を行うことが好ましい。バインダーとしてはセルロースアシレートが好ましい。紫外線吸収剤等、他の添加物と共に分散を行うことも好ましい。分散溶媒は任意であるが、ポリマー溶液溶媒と近い組成であることが好ましい。
【００５１】
微粒子粉体の数平均粒径は０．０１〜１００μｍが好ましく、０．１〜１０μｍが特に好ましい。上記の分散液はセルロースアシレート溶解工程に同時に添加しても良いし、任意の工程でポリマー溶液に添加できるが、紫外線吸収剤同様スタティックミキサ等を用い、流延直前に添加する形態が好ましい。
【００５２】
微粒子粉体の含有量は、セルロースアシレートに対して０．００１〜５質量％であることが好ましく、０．０１〜１質量％であることがより好ましい。添加量が０．００１質量％未満では添加効果を十分に発揮することができず、添加量が５質量％を超えると、外観面状が悪くなる場合がある。
【００５３】
前記離型剤としては、界面活性剤が有効であり、リン酸系、スルフォン酸系、カルボン酸系、ノニオン系、カチオン系など特に限定されない。これらは、例えば特開昭６１−２４３８３７号などに記載されている。離型剤の添加量は、セルロースアシレートに対して０．００１〜２質量％が好ましく、０．０１〜１質量％がより好ましい。添加量が０．００１質量％未満であれば添加効果を十分に発揮することができず、添加量が２質量％を超えると、析出したり、不溶解物を生じたりすることがある。
【００５４】
ノニオン系界面活性剤としては、ポリオキシエチレン、ポリオキシプロピレン、ポリオキシブチレン、ポリグリシジルやソルビタンをノニオン性親水性基とする界面活性剤であり、具体的には、ポリオキシエチレンアルキルエーテル、ポリオキシエチレンアルキルフェニールエーテル、ポリオキシエチレン−ポリオキシプロピレングリコール、多価アルコール脂肪酸部分エステル、ポリオキシエチレン多価アルコール脂肪酸部分エステル、ポリオキシエチレン脂肪酸エステル、ポリグリセリン脂肪酸エステル、脂肪酸ジエタノールアミド、トリエタノールアミン脂肪酸部分エステルを挙げることができる。
【００５５】
アニオン系界面活性剤としてはカルボン酸塩、硫酸塩、スルフォン酸塩、リン酸エステル塩であり、代表的なものとしては脂肪酸塩、アルキルベンゼンスルフォン酸塩、アルキルナフタレンスルフォン酸塩、アルキルスルフォン酸塩、α−オレフィンスルフォン酸塩、ジアルキルスルフォコハク酸塩、α−スルフォン化脂肪酸塩、Ｎ−メチルーＮオレイルタウリン、石油スルフォン酸塩、アルキル硫酸塩、硫酸化油脂、ポリオキシエチレンアルキルエーテル硫酸塩、ポリオキシエチレンアルキルフェニールエーテル硫酸塩、ポリオキシエチレンスチレン化フェニールエーテル硫酸塩、アルキルリン酸塩、ポリオキシエチレンアルキルエーテルリン酸塩、ナフタレンスルフォン酸塩ホルムアルデヒド縮合物などである。
【００５６】
カチオン系界面活性剤としてはアミン塩、４級アンモニウム塩、ピリジュム塩などを挙げることができ、第一〜第３脂肪アミン塩、第４級アンモニウム塩（テトラアルキルアンモニウム塩、トリアルキルベンジルアンモニウム塩、アルキルピリジウム塩、アルキルイミダゾリウム塩など）を挙げることができる。両性系界面活性剤としてはカルボキシベタイン、スルフォベタインなどであり、Ｎ−トリアルキル−Ｎ−カルボキシメチルアンモニウムベタイン、Ｎ−トリアルキル−Ｎ−スルフォアルキレンアンモニウムベタインなどである。
【００５７】
前記フッ素系界面活性剤を添加することにより、帯電防止効果を発揮することができる。フッ素系界面活性剤の添加量は、セルロースアシレートに対して０．００２〜２質量％が好ましく、０．０１〜０．５質量％がより好ましい。添加量が０．００２質量％未満であれば添加効果を十分に発揮することができず、添加量が２質量％を超えると、析出したり、不溶解物を生じたりすることがある。
【００５８】
本発明においては、レターデーション上昇剤（光学特性調整剤）を添加することができる。レターデーション上昇剤を添加することにより、光学異方性をコントロールすることができる。レターデーション上昇剤は、セルロースアシレートフイルムのレターデーションを調整するため、少なくとも二つの芳香族環を有する芳香族化合物を使用することが好ましい。芳香族化合物は、セルロースアシレート１００質量部に対して、０．０１〜２０質量部の範囲で使用する。芳香族化合物は、セルロースアセレート１００質量部に対して、０．０５〜１５質量部の範囲で使用することが好ましく、０．１〜１０質量部の範囲で使用することがさらに好ましい。二種類以上の芳香族化合物を併用してもよい。芳香族化合物の芳香族環には、芳香族炭化水素環に加えて、芳香族性ヘテロ環を含む。
【００５９】
芳香族炭化水素環は、６員環（すなわち、ベンゼン環）であることが特に好ましい。芳香族性ヘテロ環は一般に、不飽和ヘテロ環である。芳香族性ヘテロ環は、５員環、６員環又は７員環であることが好ましく、５員環又は６員環であることがさらに好ましい。芳香族性ヘテロ環は一般に、最多の二重結合を有する。ヘテロ原子としては、窒素原子、酸素原子及び硫黄原子が好ましく、窒素原子が特に好ましい。芳香族性ヘテロ環の例には、フラン環、チオフェン環、ピロール環、オキサゾール環、イソオキサゾール環、チアゾール環、イソチアゾール環、イミダゾール環、ピラゾール環、フラザン環、トリアゾール環、ピラン環、ピリジン環、ピリダジン環、ピリミジン環、ピラジン環及び１，３，５−トリアジン環が含まれる。
【００６０】
本発明においては、着色剤を添加することができる。着色剤を添加することにより、感光材料支持体等に用いる場合、ライトパイピングを防止することができる。着色剤の添加量は、セルロースアシレートに対する質量割合で１０〜１０００ｐｐｍが好ましく、５０〜５００ｐｐｍが更に好ましい。
【００６１】
また、本発明におけるポリマー溶液には、ルシウム、マグネシウムなどのアルカリ土類金属の塩などの熱安定剤、帯電防止剤、難燃剤、滑剤、油剤などを、必要に応じて適宜添加することができる。
【００６２】
本発明の溶液製膜方法により製造されるフィルムの光学特性について記す。まず、フィルムの面内のレターデーション（Ｒｅ）について記すと、その測定法はエリプソメーター（偏光解析計ＡＥＰ−１００：島津製作所（株）製）を用いて、波長６３２．８ｎｍにおける面内の縦横の屈折率差にフィルム膜厚さを乗じたものであり、下記の式で求められる。
Ｒｅ＝（ｎｘ−ｎｙ）×ｄ
ｎｘ：横方向の屈折率
ｎｙ：縦方向の屈折率
【００６３】
レターデーション（Ｒｅ）は、小さいほど面内方向の光学異方性がないことを示し、０〜３００ｎｍの範囲で用途に応じて用いられる。また、フィルムの厚さ方向のレターデーション（Ｒｔｈ）も重要であり、波長６３２．８ｎｍにおける厚さ方向の複屈折にフィルム膜厚さを乗じたものであり、下記の式で求められる。
Ｒｔｈ＝｛（ｎｘ＋ｎｙ）／２−ｎｚ｝×ｄ
ｎｘ：横方向の屈折率
ｎｙ：縦方向の屈折率
ｎｚ：厚さ方向の屈折率
【００６４】
厚さ方向の屈折率が小さいほど、厚さ方向の光学異方性がないことを示すが、その使用用途によって好ましい範囲は定まる。一般には、本発明により製造されたセルロースアシレートフィルムのＲｔｈは１００μｍ当たり、０ｎｍ〜６００ｎｍであり、さらには０ｎｍ〜４００ｎｍで用いられる。
【００６５】
本発明の溶液製膜方法で製造されるフィルムは、例えば、偏光板保護膜、光学補償シート、ＡＲ、ＬＲ、ＡＧ膜用支持体フィルム等の光学用途フィルム、写真感光材料用支持体フィルムとしても利用することができる。
【００６６】
本発明の溶液製膜方法で製造されるフィルムを光学補償シートに利用する場合、フイルムそのものを光学補償シートとして用いることができる。なお、フイルムそのものを光学補償シートとして用いる場合は、偏光板の透過軸と、光学補償シートの遅相軸とを実質的に平行又は垂直になるように配置することが好ましい。このような偏光板と光学補償シートとの配置については、特開平１０−４８４２０号公報に記載がある。液晶表示装置は、二枚の電極基板の間に液晶を担持してなる液晶セル、その両側に配置された二枚の偏光板、及び該液晶セルと該偏光板との間に少なくとも一枚の光学補償シートを配置した構成を有している。
【００６７】
液晶セルの液晶層は、通常は、二枚の基板の間にスペーサーを挟み込んで形成した空間に液晶を封入して形成する。透明電極層は、導電性物質を含む透明な膜として基板上に形成する。液晶セルには、さらにガスバリアー層、ハードコート層あるいは（透明電極層の接着に用いる）アンダーコート層（下塗り層）を設けてもよい。これらの層は、通常、基板上に設けられる。液晶セルの基板は、一般に５０μｍ〜２ｍｍの厚さを有する。
【００６８】
光学補償シートは複屈折性を有し、液晶表示装置の表示画面の着色を取り除いたり、視野角特性を改善したりする目的で用いられる。本発明によるセルロースアシレートフィルムそのものを、光学補償シートとして用いることができる。さらに反射防止層、防眩性層、λ／４層や２軸延伸セルロースアシレートフィルムとして機能を付与してもよい。また、液晶表示装置の視野角を改良するため、本技術のセルロースアシレートフィルムと、それとは（正／負の関係が）逆の複屈折を示すフィルムを重ねて光学補償シートとして用いてもよい。
【００６９】
また、支持体の上に液晶性化合物（特にディスコティック液晶性分子）を含む光学的異方性層を設けた光学補償シートも提案されている（特開平３−９３２５号、同６−１４８４２９号、同８−５０２０６号、同９−２６５７２号の各公報記載）。本発明の溶液製膜方法で製造されるフィルムそのような光学補償シートの支持体としても用いることができる。
【００７０】
前記偏光板の偏光素子には、ヨウ素系偏光膜、二色性染料を用いる染料系偏光膜やポリエン系偏光膜がある。いずれの偏光素子も、一般にポリビニルアルコール系フィルムを用いて製造する。偏光板の保護膜は、２５〜３５０μｍの厚さを有することが好ましく、４０〜２００μｍの厚さを有することがさらに好ましい。液晶表示装置には、表面処理膜を設けてもよい。表面処理膜の機能には、ハードコート、防曇処理、防眩処理及び反射防止処理が含まれる。
【００７１】
前記光学的異方性層は、負の一軸性を有し傾斜配向したディスコティック液晶性分子を含む層であることが好ましい。ディスコティック液晶性分子を含む層が、円盤面と支持体面とのなす角が光学的異方性層の深さ方向において変化したハイブリッド配向していても構わないし、円盤面が支持体面と平行なホメオトロピック配向、円盤面が支持体面と垂直なホモジニアス配向、又は、円盤面が光学的異方性層の深さ方向でねじれているツイスト配向を取っていても構わない。また、これらの配向が混在した配向（例えば、ハイブリッド配向＋ツイスト配向）していても構わない。そのなかでもハイブリッド配向していることが好ましい。ディスコティック液晶性分子ひとつひとつの光軸は、円盤面の法線方向に存在する。しかし、ディスコティック液晶性分子がハイブリッド配向している層全体としては、光軸は存在しない。
【００７２】
本発明の溶液製膜方法により製造されるフィルムは、様々な表示モードの液晶セルに用いることができる。ＴＮ（Ｔｗｉｓｔｅｄ Ｎｅｍａｔｉｃ）、ＩＰＳ（Ｉｎ−Ｐｌａｎｅ Ｓｗｉｔｃｈｉｎｇ）、ＦＬＣ（Ｆｅｒｒｏｅｌｅｃｔｒｉｃ Ｌｉｑｕｉｄ Ｃｒｙｓｔａｌ）、ＡＦＬＣ（Ａｎｔｉ−ｆｅｒｒｏｅｌｅｃｔｒｉｃ Ｌｉｑｕｉｄ Ｃｒｙｓｔａｌ）、ＯＣＢ（Ｏｐｔｉｃａｌｌｙ Ｃｏｍｐｅｎｓａｔｏｒｙ Ｂｅｎｄ）、ＳＴＮ（Ｓｕｐｐｅｒ Ｔｗｉｓｔｅｄ Ｎｅｍａｔｉｃ）、ＶＡ（Ｖｅｒｔｉｃａｌｌｙ Ａｌｉｇｎｅｄ）及びＨＡＮ（Ｈｙｂｒｉｄ Ａｌｉｇｎｅｄ Ｎｅｍａｔｉｃ）のような様々な表示モードが提案されている。また、上記表示モードを配向分割した表示モードも提案されている。セルロースアシレートフィルムは、いずれの表示モードの液晶表示装置においても有効である。また、透過型、反射型、半透過型のいずれの液晶表示装置においても有効である。
【００７３】
本発明の溶液製膜方法で製造されるフィルムをＴＮモードの液晶セルを有するＴＮ型液晶表示装置の光学補償シートの支持体として用いてもよい。ＴＮモードの液晶セルとＴＮ型液晶表示装置については、古くから良く知られている。ＴＮ型液晶表示装置に用いる光学補償シートについては、特開平３−９３２５号、同６−１４８４２９号、同８−５０２０６号、同９−２６５７２号の各公報に記載がある。また、モリ（Ｍｏｒｉ）他の論文（Ｊｐｎ．Ｊ．Ａｐｐｌ．Ｐｈｙｓ．Ｖｏｌ．３６（１９９７）ｐ．１４３や、Ｊｐｎ．Ｊ．Ａｐｐｌ．Ｐｈｙｓ．Ｖｏｌ．３６（１９９７）ｐ．１０６８）に記載がある。ＴＮ型液晶表示装置については、特開平１０−１２３４７８号、ＷＯ９８４８３２０号、特許第３０２２４７７号の各公報に記載がある。
【００７４】
本発明の溶液製膜方法で製造されるフィルムをＳＴＮモードの液晶セルを有するＳＴＮ型液晶表示装置の光学補償シートの支持体として用いてもよい。一般的にＳＴＮ型液晶表示装置では、液晶セル中の棒状液晶性分子が９０〜３６０度の範囲にねじられており、棒状液晶性分子の屈折率異方性（Δｎ）とセルギャップ（ｄ）との積（Δｎｄ）が３００〜１５００ｎｍの範囲にある。ＳＴＮ型液晶表示装置に用いる光学補償シートについては、特開２０００−１０５３１６号公報に記載がある。
【００７５】
本発明の溶液製膜方法で製造されるフィルムをＶＡモードの液晶セルを有するＶＡ型液晶表示装置の光学補償シートの支持体として用いてもよい。ＶＡ型液晶表示装置に用いる光学補償シートには、レターデーションの絶対値が最小となる方向が光学補償シートの面内にも法線方向にも存在しないことが好ましい。ＶＡ型液晶表示装置に用いる光学補償シートの光学的性質は、光学的異方性層の光学的性質、支持体の光学的性質及び光学的異方性層と支持体との配置により決定される。ＶＡ型液晶表示装置に光学補償シートを二枚使用する場合は、光学補償シートの面内レターデーションを、−５ｎｍ〜５ｎｍの範囲内にすることが好ましい。従って、二枚の光学補償シートのそれぞれの面内レターデーションの絶対値は、０〜５とすることが好ましい。ＶＡ型液晶表示装置に光学補償シートを一枚使用する場合は、光学補償シートの面内レターデーションを、−１０ｎｍ〜１０ｎｍの範囲内にすることが好ましい。
【００７６】
本発明の溶液製膜方法で製造されるフィルムを、ＯＣＢモードの液晶セルを有するＯＣＢ型液晶表示装置あるいはＨＡＮモードの液晶セルを有するＨＡＮ型液晶表示装置の光学補償シートの支持体として用いてもよい。ＯＣＢ型液晶表示装置あるいはＨＡＮ型液晶表示装置に用いる光学補償シートには、レターデーションの絶対値が最小となる方向が光学補償シートの面内にも法線方向にも存在しないことが好ましい。ＯＣＢ型液晶表示装置あるいはＨＡＮ型液晶表示装置に用いる光学補償シートの光学的性質も、光学的異方性層の光学的性質、支持体の光学的性質及び光学的異方性層と支持体との配置により決定される。ＯＣＢ型液晶表示装置あるいはＨＡＮ型液晶表示装置に用いる光学補償シートについては、特開平９−１９７３９７号公報に記載がある。また、モリ（Ｍｏｒｉ）他の論文（Ｊｐｎ．Ｊ．Ａｐｐｌ．Ｐｈｙｓ．Ｖｏｌ．３８（１９９９）ｐ．２８３７）に記載がある。
【００７７】
本発明の溶液製膜方法で製造されるフィルムをＡＳＭ（Ａｘｉａｌｌｙ Ｓｙｍｍｅｔｒｉｃ Ａｌｉｇｎｅｄ Ｍｉｃｒｏｃｅｌｌ）モードの液晶セルを有するＡＳＭ型液晶表示装置の光学補償シートの支持体として用いてもよい。ＡＳＭモードの液晶セルは、セルの厚さが位置調整可能な樹脂スペーサーにより維持されているとの特徴がある。その他の性質は、ＴＮモードの液晶セルと同様である。ＡＳＭモードの液晶セルとＡＳＭ型液晶表示装置については、クメ（Ｋｕｍｅ）外の論文（Ｋｕｍｅ ｅｔ ａｌ．，ＳＩＤ ９８ Ｄｉｇｅｓｔ １０８９（１９９８））に記載がある。
【００７８】
【実施例】
溶液製膜工程において、使用した原料は以下の通りである。
セルローストリアセテート １００重量部
トリフェニルフォスフェート １０重量部
ビフェニルジフェニルフォスフェート ５重量部
メチレンクロライド ３１５重量部
メタノール ６０重量部
ｎ−ブタノール １０重量部
【００７９】
共流延時の副流ポリマー溶液組成
セルローストリアセテート １００重量部
トリフェニルフォスフェート １０重量部
ビフェニルジフェニルフォスフェート ５重量部
メチレンクロライド ４００重量部
メタノール ７５重量部
ｎ−ブタノール １３重量部
実施例の各条件にて、エアー同伴有無、流延リボンの安定性を観察した。
【００８０】
［実施例１］
下記の条件で、製膜を行った。
１）流延ダイと支持体の距離ｈ＝３ｍｍ
２）流延速度ｖ＝４５ｍ／分
３）ベース厚みｔ＝８０μｍ
４）バックサクション静圧ｐ＝−３０Ｐａ
５）バックサクション装置と流延バンドの間隔ｄ＝１．０ｍｍ
エアー同伴は発生せず、流延リボンは安定していた。
【００８１】
［実施例２］
下記の条件で、共流延法により製膜を行った。
１）流延ダイと支持体の距離ｈ＝３ｍｍ
２）流延速度ｖ＝４５ｍ／分
３）ベース厚みｔ＝８０μｍ，主流厚み＝７６μｍ，副流厚み（上下層）＝各２μｍ
４）バックサクション静圧ｐ＝−３０Ｐａ
５）バックサクション装置と流延バンドの間隔ｄ＝１．０ｍｍ
エアー同伴は発生せず、流延リボンは安定していた。
【００８２】
［実施例３］
ポリマー溶液処方を変えて、下記の条件で製膜を行った。
セルローストリアセテート １００重量部
トリフェニルフォスフェート １０重量部
ビフェニルジフェニルフォスフェート ５重量部
酢酸メチル ３１５重量部
エタノール ６０重量部
ｎ−ブタノール １０重量部
【００８３】
溶媒にてセルローストリアセテートを３０分間膨潤させ、−７０℃にて冷却後５０℃に加温溶解した。
１）流延ダイと支持体の距離ｈ＝３ｍｍ
２）流延速度ｖ＝４５ｍ／分
３）ベース厚みｔ＝８０μｍ
４）バックサクション静圧ｐ＝−３０Ｐａ
５）バックサクション装置と流延バンドの間隔ｄ＝１．０ｍｍ
エアー同伴は発生せず、流延リボンは安定していた。
【００８４】
［比較例１］
下記の条件で、製膜を行った。
１）流延ダイと支持体の距離ｈ＝３ｍｍ
２）流延速度ｖ＝４５ｍ／分
３）ベース厚みｔ＝８０μｍ
４）バックサクション無し
エアー同伴が発生し、流延続行不可能であった。
【００８５】
［比較例２］
下記の条件で、製膜を行った。
１）流延ダイと支持体の距離ｈ＝３ｍｍ
２）流延速度ｖ＝４５ｍ／分
３）ベース厚みｔ＝８０μｍ
４）バックサクション静圧ｐ＝−２Ｐａ
５）バックサクション装置と流延バンドの間隔ｄ＝１．０ｍｍ
エアー同伴が発生し、流延続行不可能であった。
【００８６】
［比較例３］
下記の条件で、製膜を行った。
１）流延ダイと支持体の距離ｈ＝３ｍｍ
２）流延速度ｖ＝４５ｍ／分
３）ベース厚みｔ＝８０μｍ
４）バックサクション静圧ｐ＝−３０Ｐａ
５）バックサクション装置と流延バンドの間隔ｄ＝３．５ｍｍ
エアー同伴は発生しなかったが、流延リボンの揺れが発生し安定しなかった。
【００８７】
［偏光板の耐久性評価］
実施例１〜３の方法で製膜したフィルムを偏光板保護膜とする偏光板を作製し、耐久性を評価した。
【００８８】
＜偏光板の作成方法＞
偏光板サンプルは、ポリビニルアルコールを延伸してヨウ素を吸着させた偏光素子の両面にポリビニルアルコール系接着剤により貼り合わせし作製した。この偏光板サンプルを６０℃、９０％ＲＨの雰囲気下で５００時間暴露した。いずれにおいても、偏光度は９９．６％以上であり、十分な耐久性が認められた。
【００８９】
＜偏光度の評価方法＞
分光光度計により可視領域における並行透過率Ｙｐ、直交透過率Ｙｃを求め、次式に基づき偏光度Ｐを決定する。
Ｐ＝√（（Ｙｐ−Ｙｃ）／（Ｙｐ＋Ｙｃ））
【００９０】
［実施例４］
＜セルローストリアセテート溶液の作製＞
攪拌羽根を有するステンレス性溶解タンクに、下記の溶媒混合溶液によく攪拌しつつ、セルローストリアセテート粉体（平均サイズ２ｍｍ）を徐々に添加し、仕込んだ。添加後、室温（２５℃）にて３時間，２５℃にて放置し、セルローストリアセテートを膨潤させた。なお、溶媒である酢酸メチルとシクロペンタノン、アセトン、メタノール及びエタノールは、すべてその含水率が０．２質量％以下のものを利用した。
【００９１】
セルローストリアセテート １６質量部
（置換度２．８３、粘度平均重合度３２０、含水率０．４質量％、メチレンクロライド溶液中６質量％の粘度３０５ｍＰａ・ｓ）
酢酸メチル ５３質量部
シクロペンタン １０質量部
アセトン ５質量部
メタノール ５質量部
エタノール ５質量部
可塑剤Ａ（ジペンタエリスリトールヘキサアセテート） ３質量部
可塑剤Ｂ（トリフェニルフォスフェート） ３質量部
微粒子粉体（シリカ（粒径２０ｎｍ）） ０．１質量部
紫外線吸収剤ａ ０．１質量部
（２，４−ビス−（ｎ−オクチルチオ）−６−（４−ヒドロキシ−３，５−ジ−ｔｅｒｔ−ブチルアニリノ）−１，３，５−トリアジン）
紫外線吸収剤ｂ ０．１質量部
（２（２’−ヒドロキシ−３’，５’−ジ−ｔｅｒｔ−ブチルフェニル）−５−クロルベンゾトリアゾール）
紫外線吸収剤ｃ ０．１質量部
（２（２’−ヒドロキシ−３’，５’−ジ−ｔｅｒｔ−アミルフェニル）−５−クロルベンゾトリアゾール
Ｃ₁₂Ｈ₂₅ＯＣＨ₂ＣＨ₂Ｏ−Ｐ(＝Ｏ)−(ＯＫ)₂ ０．０５質量部
【００９２】
なお、後述する冷却溶解法で得られたこの溶液の粘度は１６０Ｐａ・Ｓ（４５℃）であった。
【００９３】
＜セルローストリアセテート溶液の冷却溶解＞
上述したセルローストリアセテート溶液をスクリュー押し出し機で送液して、−７０℃で３分間となるように冷却部分を通過させた。冷却は冷凍機で冷却した−８０℃の冷媒（３Ｍ社製，『フロリナート』）を用いて実施した。そして、冷却により得られた溶液は、静止型混合器を設置した熱交換器により１２０℃まで温度を上昇させ、３分間保持した後冷却し５０℃としてステンレス製の容器に移送し、５０℃で２時間撹拌し脱泡を行った。このように調製したセルローストリアセテート溶液を、絶対濾過精度０．０１ｍｍの濾紙（東洋濾紙（株）製，『＃６３』）で濾過し、さらに、絶対濾過精度０．００２５ｍｍの濾紙（ポール社製，『ＦＨ ０２５』）にて濾過した。
【００９４】
＜セルローストリアセテートフィルムの作製＞
上述した溶解法で得られたセルローストリアセテート溶液を５０℃にし、流延ギーザ−を通して鏡面ステンレスの流延支持体上に流延した。乾燥は１２０℃の乾燥風を送風した。２分後に鏡面ステンレスの流延支持体から剥ぎ取り、その後、１１０℃、１０分、さらに１５０℃で３０分乾燥して、セルローストリアセテートフィルム（膜厚４０μｍ）を得た。
【００９５】
下記の条件で、製膜を行った。
１）流延ダイと支持体の距離ｈ＝２ｍｍ
２）流延速度ｖ＝４０ｍ／分
３）ベース厚みｔ＝４０μｍ
４）バックサクション静圧ｐ＝−１００Ｐａ
５）バックサクション装置と流延バンドの間隔ｄ＝０．５ｍｍ
６）塗布幅＝１００ｃｍ
７）流延支持体温度＝１０℃
エアー同伴は発生せず、流延リボンは安定していた。
【００９６】
＜偏光板ａの作製＞
延伸したポリビニルアルコールフィルムにヨウ素を吸着させて偏光素子を作製し、ポリビニルアルコール系接着剤を用いて、上記セルローストリアセテートフィルムを、その遅相軸が偏光素子の透過軸と平行になるように両側に貼り付けた。
【００９７】
この偏光板ａを８０℃、９０ＲＨの雰囲気下で５００時間暴露し、上述した方法で偏光度を測定した。偏光度は９９．６％以上であり、十分な耐久性が認められた。
【００９８】
＜偏光板ｂの作製＞
延伸したポリビニルアルコールフィルムにヨウ素を吸着させて偏光素子を作製し、ポリビニルアルコール系接着剤を用いて、上記セルローストリアセテートフィルムを、その遅相軸が偏光膜の透過軸と平行になるように片側に貼り付けるとともに、上記セルローストリアセテートフィルムにケン化処理を行い、ポリビニルアルコール系接着剤を用いて、偏光膜の反対側に貼り付けた。さらに、光学補償シート（富士写真フイルム（株）製，『ＷＶフィルム』）をセルローストリアセテートフィルム側に、その遅相軸が互いに平行になるように粘着剤を用いて貼り付け、光学補償シートを貼合した偏光板を作製した。
【００９９】
この偏光板ｂを８０℃、９０ＲＨの雰囲気下で５００時間暴露し、上述した方法で偏光度を測定した。偏光度は９９．６％以上であり、十分な耐久性が認められた。
【０１００】
＜液晶表示装置での評価＞
上記偏光板ａ及び偏光板ｂをＴＦＴ（薄膜トランジスター）方式の液晶表示装置に実装した。その結果、良好な視野角及びコントラストを得ることができた。
【０１０１】
［実施例５］
＜内層用セルローストリアセテート溶液の作製＞
攪拌羽根を有するステンレス性溶解タンクに、下記の溶剤混合溶液によく攪拌しつつ、セルローストリアセテート粉体（平均サイズ２ｍｍ）を徐々に添加して仕込んだ。添加後、室温（２５℃）にて３時間放置し、セルローストリアセテートを膨潤させた。なお、溶剤である酢酸メチルとシクロペンタノン、アセトン、メタノール及びエタノールは、すべてその含水率が０．２質量％以下のものを利用した。
【０１０２】
セルローストリアセテート １６質量部
（置換度２．８３、粘度平均重合度３２０、含水率０．４質量％、メチレンクロライド溶液中６質量％の粘度３０５ｍＰａ・ｓ）
酢酸メチル ５３質量部
シクロペンタン １０質量部
アセトン ５質量部
メタノール ５質量部
エタノール ５質量部
可塑剤Ａ（ジペンタエリスリトールヘキサアセテート） ３質量部
可塑剤Ｂ（トリフェニルフォスフェート） ３質量部
微粒子粉体（シリカ（粒径２０ｎｍ）） ０．１質量部
紫外線吸収剤ａ ０．１質量部
（２，４−ビス−（ｎ−オクチルチオ）−６−（４−ヒドロキシ−３，５−ジ−ｔｅｒｔ−ブチルアニリノ）−１，３，５−トリアジン）
紫外線吸収剤ｂ ０．１質量部
（２（２’−ヒドロキシ−３’，５’−ジ−ｔｅｒｔ−ブチルフェニル）−５−クロルベンゾトリアゾール）
紫外線吸収剤ｃ ０．１質量部
（２（２’−ヒドロキシ−３’，５’−ジ−ｔｅｒｔ−アミルフェニル）−５−クロルベンゾトリアゾール
Ｃ₁₂Ｈ₂₅ＯＣＨ₂ＣＨ₂Ｏ−Ｐ(＝Ｏ)−(ＯＫ)₂ ０．０５質量部
【０１０３】
なお、冷却溶解法で得られたこの溶液の粘度は６０Ｐａ・Ｓ（４５℃）であった。
【０１０４】
＜内層用セルローストリアセテート溶液の冷却溶解＞
上述したセルローストリアセテート溶液をスクリュー押し出し機で送液して、−７０℃で３分間となるように冷却部分を通過させた。冷却は冷凍機で冷却した−８０℃の冷媒（３Ｍ社製，『フロリナート』）を用いて実施した。そして、冷却により得られた溶液は静止型混合器を設置した熱交換器により１２０℃まで温度を上昇させ、３分間保持した後、冷却し５０℃としてステンレス製の容器に移送し、５０℃で２時間撹拌し脱泡を行った。このセルローストリアセテート溶液を絶対濾過精度０．０１ｍｍの濾紙（東洋濾紙（株）製，『＃６３』）で濾過し、さらに、絶対濾過精度０．００２５ｍｍの濾紙（ポール社製，『ＦＨ ０２５』）で濾過した。
【０１０５】
＜外層用セルローストリアセテート溶液の調整＞
上述した内層用セルローストリアセテート溶液において、セルローストリアセテートを１９質量部、酢酸メチルを４４質量部に変更した他は、同様に仕込んだ。なお、冷却溶解法で得られたこの溶液の粘度は２５Ｐａ・Ｓ（４５℃）であった。
【０１０６】
＜外層用セルローストリアセテート溶液の冷却溶解＞
上述したセルローストリアセテート溶液をスクリュー押し出し機で送液して、−７０℃で３分間となるように冷却部分を通過させた。冷却は冷凍機で冷却した−８０℃の冷媒（３Ｍ社製，『フロリナート』）を用いて実施した。そして、冷却により得られた溶液は静止型混合器を設置した熱交換器により１２０℃まで温度を上昇させ、３分間保持した後、冷却し５０℃としてステンレス製の容器に移送し、５０℃で２時間撹拌し脱泡を行った。このセルローストリアセテート溶液を絶対濾過精度０．０１ｍｍの濾紙（東洋濾紙（株）製，『＃６３』）で濾過し、さらに、絶対濾過精度０．００２５ｍｍの濾紙（ポール社製，『ＦＨ ０２５』）で濾過した。
【０１０７】
＜セルローストリアセテートフィルムの作製＞
上述したセルローストリアセテート溶液を三層共流延ダイを用い、内層用セルローストリアセテート溶液が内側に、外層用セルローストリアセテート溶液が両外側になるように配置して、金属ならなる流延支持体上に同時に吐出させて重層流延した後、流延膜を流延支持体から剥ぎ取り、乾燥して三層構造のセルローストリアセテートフィルム積層体（内層の厚さ：８０μｍ、各表面層の厚さ：２μｍ）を作製した。
【０１０８】
下記の条件で、製膜を行った。
１）流延ダイと支持体の距離ｈ＝５ｍｍ
２）流延速度ｖ＝５０ｍ／分
３）ベース厚みｔ＝８４μｍ
４）バックサクション静圧ｐ＝−５０Ｐａ
５）バックサクション装置と流延バンドの間隔ｄ＝１．０ｍｍ
６）塗布幅＝１００ｃｍ
７）流延支持体温度＝１０℃
エアー同伴は発生せず、流延リボンは安定していた。
【０１０９】
流延支持体から剥ぎ取ったフィルムは、テンターにより搬送しつつ乾燥させ、１００℃で３分、１３０℃で５分乾燥させた後、１５０℃で１０分で段階的に乾燥させて溶剤を蒸発させてセルローストリアセテートフィルムを得た。
【０１１０】
＜偏光板ｃの作製＞
延伸したポリビニルアルコールフィルムにヨウ素を吸着させて偏光素子を作製し、ポリビニルアルコール系接着剤を用いて、上記セルローストリアセテートフィルムを、その遅相軸が偏光素子の透過軸と平行になるように両側に貼り付けた。この偏光板ｃを８０℃、９０ＲＨの雰囲気下で５００時間暴露し、上述した方法で偏光度を測定した。偏光度は９９．６％以上であり、十分な耐久性が認められた。
【０１１１】
＜偏光板ｄの作製＞
延伸したポリビニルアルコールフィルムにヨウ素を吸着させて偏光素子を作製し、ポリビニルアルコール系接着剤を用いて、上記セルローストリアセテートフィルムを、その遅相軸が偏光素子の透過軸と平行になるように片側に貼り付けるとともに、上記セルローストリアセテートフィルムにケン化処理を行い、ポリビニルアルコール系接着剤を用いて、偏光素子の反対側に貼り付けた。さらに、光学補償シート（富士写真フイルム（株）製，『ＷＶフィルム』）をセルローストリアセテートフィルム側に、その遅相軸が互いに平行になるように粘着剤を用いて貼り付け、光学補償シートを貼合した偏光板を作製した。
【０１１２】
この偏光板ｄを８０℃、９０ＲＨの雰囲気下で５００時間暴露し、上述した方法で偏光度を測定した。偏光度は９９．６％以上であり、十分な耐久性が認められた。
【０１１３】
＜液晶表示装置での評価＞
上記偏光板ｃ及び偏光板ｄをＴＦＴ（薄膜トランジスター）方式の液晶表示装置に実装した。その結果、良好な視野角及びコントラストを得ることができた。
【０１１４】
【発明の効果】
本発明により、流延バンドを用いてセルロースアセテートフィルムを製造する生産効率を向上させることができる。
【図面の簡単な説明】
【図１】 溶液製膜装置の流延ダイ部分の模式図である。
【図２】 本発明の溶液製膜方法を実施する溶液製膜装置の模式図である。
【図３】 図１の流延ダイ部分の平面図である。
【図４】 同上バックサクション装置の底面図である。
【図５】 本発明の溶液製膜方法を実施する溶液製膜装置に用いる流延ダイの模式断面図である。
【図６】 本発明の溶液製膜方法を実施する溶液製膜装置に用いる流延ダイの模式断面図である。
【図７】 本発明の溶液製膜方法を実施する溶液製膜装置に用いる流延ダイの模式断面図である。
【符号の説明】
１…リボン状ポリマー溶液
２…支持体
３…減圧チャンバー
４…リボン
１０…流延ダイ
１１…マニホールド
１２…マニホールド
１３…マニホールド
１４…フィードブロック
２０…回転ドラム
２１…剥取ローラ
３０…流延バンド（支持体）
４０…バックサクション装置
４１…減圧チャンバー
４２…減圧チャンバー
４３…吸引ダクト接続口
４４…仕切り
４５…ラビリンス
５０…吸引ダクト
６０…バッファータンク
７０…ブロワー
８０…流延ドラム[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a solution casting method capable of producing a cellulose acetate film such as cellulose triacetate at high speed using a casting band.
[0002]
[Prior art]
Films for optical uses and the like are manufactured based on a film such as cellulose triacetate, and the film such as cellulose triacetate is manufactured by a solution casting method. In the solution casting method, a polymer solution dissolved in an organic solvent is cast from a die onto a support, and a ribbon (liquid film from the die discharge port to the support landing. The same) is in close contact with the support. As such a solution casting method, for example, in Japanese Examined Patent Publication No. 49-36946, a vacuum chamber having two suction chambers is provided to prevent air entrainment, and the liquid composition and the roller are brought into close contact with each other. A method of casting a liquid composition has been proposed. In Japanese Patent Publication No. 62-38133 and Japanese Patent Publication No. 63-57222, a web of a web that can stabilize an end bead by providing two vacuum zones with an isolation wall. Uniform pressing devices have been proposed. US Pat. No. 4,310,295 discloses a method for uniformly fixing a web by preventing edge leak air.
[0003]
[Problems to be solved by the invention]
Even in the production of cast cellulose acetate film, high speed is required to improve production efficiency. The problem of speeding up in this cellulose acetate casting is the air entrainment phenomenon. In order to prevent this, the viscosity or concentration of the polymer solution is reduced, or the back suction method is used. However, lowering the viscosity and lowering the concentration tend to cause an increase in the drying load after casting the film on the support, and to cause wind unevenness and drying unevenness due to the drying air, which significantly impairs the quality of the film forming film. On the other hand, in the back suction method, if the gap between the support and the support is wide, the stability of the casting ribbon is disturbed due to the influence of the inflow air due to the back suction, and if it is narrow, the decompression chamber and the support come into contact with each other. I was hurt. The method using a casting band can make the drying time on the support longer than the method using a casting drum, so that the flatness of the film is excellent. Usually, the backband chamber was not used in the extension band.
[0004]
An object of the present invention is to provide a method capable of increasing the production rate in a method for producing a cellulose acetate film using a casting band.
[0005]
[Means for Solving the Problems]
As a result of intensive studies to improve the productivity of the casting band method in which the flatness of the film is superior to that of the casting drum method, the present inventors have developed a back suction device while being narrow in the casting band. It has been found that there is an area where it can be installed and produce film stably. Further, at that time, it has been found that there is a preferable pressure range of back suction, and there is also a preferable structure in the back suction device itself.
[0006]
That is, the present invention In the solution casting method using a casting band, a back suction device is provided behind the casting die, the distance between the back suction device and the casting band is 0.3 to 3 mm, and the back suction device is A front decompression chamber disposed on the downstream side, a rear decompression chamber disposed on the upstream side, and a suction duct connected near both side ends of the upper surface of the rear decompression chamber. A method for forming a cellulose acetate solution, wherein the vacuum chamber and the vacuum chamber on the rear side are partitioned by a partition and communicate with each other only by a gap between the casting band. Is to provide.
[0007]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 2 shows a schematic structure of a solution casting apparatus using a casting band having a mirror-finished surface for carrying out the solution casting method of the present invention.
[0008]
In the band-type solution casting apparatus shown in FIG. 2, reference numeral 10 denotes a casting die, and a rotating drum 20 is provided facing the casting die 10, and the casting band 30 is wound around the rotating drum 20. It is designed to be hung and run. Further, a back suction device 40 is provided adjacent to the casting die 10, and the back suction device 40 is connected to the blower 70 via a suction duct 50 and a buffer tank 60. Reference numeral 21 denotes a peeling roller.
[0009]
A partially enlarged view of the vicinity of the back suction device 40 is shown in FIG. The back suction device 40 sucks the ribbon-shaped polymer solution 1 cast from the casting die 10 from behind and makes the polymer solution cast and adhere to the support while preventing air entrainment.
[0010]
The back suction device has a box-like structure as a whole with a side surface corresponding to the casting die.
[0011]
A plan view of a portion corresponding to FIG. 1 is shown in FIG. 3, and a bottom view of the back suction device is shown in FIG. This back suction device is closed on the top, front, rear and both sides, and only the bottom is open.
This back suction device is provided for the entire width of the casting die discharge.
[0012]
In the back suction device of FIG. 1, the decompression chambers 41 and 42 are divided into two chambers in the width direction, and the connection ports 43 of the suction duct are provided one by one near the both side ends of the upper surface of the rear decompression chamber 42. Yes. A partition 44 for partitioning both the decompression chambers 41 and 42 is a flat plate that partitions the chambers 41 and 42 from the upper end to the lower end. Accordingly, the front decompression chamber 41 is closed at the front, back, left, and right, and the top surface, and the decompression is performed by transmitting the decompression of the rear decompression chamber 42 through the gap between the bottom surface and the casting band 30 or the casting drum 80. Done. The entire bottom surface of the decompression chamber 42 on the rear side is an opening. Thus, by dividing the decompression chambers 41 and 42 into two chambers, the wind between the suction duct and the ribbon-like polymer solution is shielded to reduce the influence of the wind.
[0013]
It is preferable that the end portion in the width direction of the back suction chamber has a labyrinth structure. In FIG. 4, labyrinths 45 are provided at both ends of the front decompression chamber 41. Each labyrinth is a flat plate that is partitioned from the upper end of the decompression chamber 41 to substantially the lower end. This labyrinth suppresses the flow of wind at both ends and reduces eddy currents.
[0014]
The distance between the bottom surface of the back suction device 40 and the surface of the casting band 30 is 0.3 to 3 mm, preferably 0.5 to 1.5 mm. If the width is smaller than 0.3 mm, the bottom surface of the back suction device may rub against the surface of the support, and if it is larger than 3 mm, the amount of air flowing into the back suction device due to decompression increases and the ribbon is cast. Causes the polymer solution to become unstable.
[0015]
The static pressure of the back suction is −10 to −500 Pa, preferably −10 to −100 Pa.
[0016]
The distance h between the casting die and the support is usually set in the range of 1 mm to 10 mm, preferably in the range of 1.5 mm to 6 mm, but is not limited thereto.
[0017]
The polymer solution viscosity is usually set in the range of 10p to 1000p, and preferably in the range of 100p to 800p, but is not limited thereto.
[0018]
The lip clearance cl is usually set in the range of 0.2 mm to 3 mm, and preferably in the range of 0.5 mm to 2 mm, but is not limited thereto.
[0019]
The casting speed v is usually set in the range of 3 m / min to 150 m / min, preferably in the range of 10 m / min to 100 m / min, but is not limited thereto.
[0020]
The thickness t of the film is preferably 20 to 500 μm, more preferably 30 to 300 μm, and most preferably 35 to 200 μm, but is not limited thereto.
[0021]
As the casting die, those shown in FIGS. 5, 6 and 7 can be used.
[0022]
FIG. 5 shows a casting die used for forming a single-layer film. The casting die 10 has a single manifold 11. FIG. 6 shows a multi-manifold type co-casting die. The co-casting die 10 has three manifolds 12 and can form a film having a three-layer structure. FIG. 7 shows a feed block type co-casting die. The co-casting die 10 is provided with a manifold 13 and a feed block 14 which are joined together in the feed block 14 to form a plurality of layers (FIG. 7). In this case, a polymer solution having three layers is cast.
[0023]
In the above casting die, a coat hanger die is used, but the present invention is not limited to this, and a die having another shape such as a T die may be used.
[0024]
Cellulose acylate is used as the material polymer of the polymer solution used in the solution casting method of the present invention. Details of the cellulose acylate are described below. Preferred cellulose acylates are those in which the substitution degree of the hydroxyl group of cellulose satisfies all of the following formulas (1) to (4).
(1) 2.6 ≦ A + B ≦ 3.0
(2) 2.0 ≦ A ≦ 3.0
(3) 0 ≦ B ≦ 0.8
(4) 1.9 <AB
[0025]
Here, A and B represent the substituent of the acyl group substituted by the hydroxyl group of cellulose, A is the substitution degree of an acetyl group, and B is the substitution degree of a C3-C5 acyl group. . Cellulose has three hydroxyl groups in one glucose unit, and the above number represents the degree of substitution with respect to the hydroxyl group 3.0, and the maximum degree of substitution is 3.0. Cellulose triacetate generally has a substitution degree of A of 2.6 or more and 3.0 or less (in this case, there is a maximum of 0.4 hydroxyl groups not substituted), and B = 0 is cellulose triacetate. The cellulose acylate used in the polymer solution of the solution film-forming method of the present invention is cellulose triacetate whose acyl groups are all acetyl groups, and an acetyl group of 2.0 or more and an acyl group of 3 to 5 carbon atoms is 0.00. It is preferably 8 or less and an unsubstituted hydroxyl group of 0.4 or less, particularly preferably cellulose triacetate having a substitution degree of 2.6 to 3.0. The degree of substitution can be obtained by calculation by measuring the degree of binding of acetic acid substituted with a hydroxyl group of cellulose and a fatty acid having 3 to 5 carbon atoms. As a measuring method, it can carry out according to ASTM D-817-91.
[0026]
Other acyl groups having 3 to 5 carbon atoms of the acetyl group are propionyl groups (C ₂ H ₅ CO-), butyryl group (C ₃ H ₇ CO-) (n-, iso-), valeryl group (C ₄ H ₉ CO-) (n-, iso-, sec-, tert-), of which n-substituted ones are preferred from the viewpoint of mechanical strength when formed into a film, ease of dissolution, etc., and in particular, an n-propionyl group Is preferred. Moreover, when the substitution degree of an acetyl group is low, mechanical strength and heat-and-moisture resistance deteriorate. When the degree of substitution of the acyl group having 3 to 5 carbon atoms is high, the solubility in an organic solvent is improved. However, if the degree of substitution is within the above range, good physical properties are exhibited.
[0027]
The degree of polymerization (average viscosity) of cellulose acylate is preferably from 200 to 700, particularly preferably from 250 to 550. The viscosity average degree of polymerization (DP) can be determined with an Ostwald viscometer, and is determined from the measured intrinsic viscosity [η] of cellulose acylate according to the following formula.
DP = [η] / Km (where Km is a constant 6 × 10 ^-4 )
[0028]
Examples of cellulose as a cellulose acylate raw material include cotton linter and wood pulp. Any cellulose acylate obtained from any raw material cellulose may be used, or these may be used in combination.
[0029]
Examples of organic solvents that dissolve cellulose acylate include hydrocarbons (eg benzene, toluene), halogenated hydrocarbons (eg methylene chloride, chlorobenzene), alcohols (eg methanol, ethanol, diethylene glycol), ketones (eg : Acetone), esters (eg, methyl acetate, ethyl acetate, propyl acetate) and ethers (eg, tetrahydrofuran, methyl cellosolve) and the like.
[0030]
A halogenated hydrocarbon having 1 to 7 carbon atoms is preferably used, and methylene chloride is most preferably used. From the viewpoint of physical properties such as solubility of cellulose acylate, peelability from the support, mechanical strength of the film, optical properties, etc., in addition to methylene chloride, one or several alcohols having 1 to 5 carbon atoms are mixed. It is preferable. 2-25 mass% is preferable with respect to the whole solvent, and, as for content of alcohol, 5-20 mass% is more preferable. Specific examples of the alcohol include methanol, ethanol, n-propanol, isopropanol, n-butanol, etc., but methanol, ethanol, n-butanol, or a mixture thereof is preferably used.
[0031]
Moreover, it is preferable to use the solvent which consists of methyl acetate, a ketone, and alcohol and the solvent ratio is 20-90 mass% of methyl acetate, 5-60 mass% of ketone, and 5-30 mass% of alcohol.
[0032]
Recently, a solvent composition not using methylene chloride has been proposed in order to minimize the influence on the environment. For this purpose, ethers having 3 to 12 carbon atoms, ketones having 3 to 12 carbon atoms, and esters having 3 to 12 carbon atoms are preferable, and these are used by appropriately mixing them. These ethers, ketones and esters may have a cyclic structure. A compound having two or more functional groups of ether, ketone and ester (that is, —O—, —CO— and —COO—) can also be used as the organic solvent. The organic solvent may have another functional group such as an alcoholic hydroxyl group. In the case of an organic solvent having two or more types of functional groups, the number of carbon atoms may be within the specified range of the compound having any functional group.
[0033]
Examples of ethers having 3 to 12 carbon atoms include diisopropyl ether, dimethoxymethane, dimethoxyethane, 1,4-dioxane, 1,3-dioxolane, tetrahydrofuran, anisole and phenetole. Examples of ketones having 3 to 12 carbon atoms include acetone, methyl ethyl ketone, diethyl ketone, diisobutyl ketone, cyclopentanone, cyclohexanone and methylcyclohexanone. Examples of the esters having 3 to 12 carbon atoms include ethyl formate, propyl formate, pentyl formate, methyl acetate, ethyl acetate and pentyl acetate. Examples of the organic solvent having two or more kinds of functional groups include 2-ethoxyethyl acetate, 2-methoxyethanol and 2-butoxyethanol.
[0034]
In a system that cannot be easily dissolved at room temperature and a system that contains a large amount of insoluble matter, a good polymer solution can be prepared by using cooling or heating at the time of dissolution or a combination of both. In the cooling dissolution method, dissolution is accelerated by allowing a solvent to rapidly and effectively penetrate into the polymer. The effective temperature condition is −100 to −10 ° C., and a polymer solution with better solubility can be obtained by heating to room temperature to 200 ° C. after cooling.
[0035]
In the polymer solution used in the solution casting method of the present invention, various additives (for example, plasticizers, ultraviolet absorbers, deterioration inhibitors, fine particle powders, mold release agents, optical properties) according to the use in each preparation step. Regulators, fluorosurfactants) can be added. Moreover, the addition time may be added at any time in the polymer solution preparation step, but the addition may be carried out by adding an additive to the final preparation step of the polymer solution preparation step.
[0036]
As the plasticizer, phosphoric acid ester or carboxylic acid ester is used. Examples of phosphate esters include triphenyl phosphate (TPP) and tricresyl phosphate (TCP), cresyl diphenyl phosphate, octyl diphenyl phosphate, diphenyl biphenyl phosphate, trioctyl phosphate, tributyl phosphate, etc. Is given. Representative examples of the carboxylic acid ester include phthalic acid esters and citric acid esters. Examples of phthalic acid esters include dimethyl phthalate (DMP), diethyl phthalate (DEP), dibutyl phthalate (DBP), dioctyl phthalate (DOP), diphenyl phthalate (DPP) and diethyl hexyl phthalate (DEHP). Examples of citrate esters include triethyl O-acetylcitrate (OACTE) and tributyl O-acetylcitrate (OACTB), acetyltriethyl citrate, and acetyltributyl citrate.
[0037]
Examples of other carboxylic acid esters include trimellitic acid esters such as butyl oleate, methyl acetyl ricinoleate, dibutyl sebacate, and trimethyl trimellitate. Examples of glycolic acid esters include triacetin, tributyrin, butyl phthalyl butyl glycolate, ethyl phthalyl ethyl glycolate, methyl phthalyl ethyl glycolate, and butyl phthalyl butyl glycolate.
[0038]
Among the plasticizers exemplified above, triphenyl phosphate, biphenyl diphenyl phosphate, tricresyl phosphate, cresyl diphenyl phosphate, tributyl phosphate, dimethyl phthalate, diethyl phthalate, dibutyl phthalate, dioctyl phthalate, diethyl hexyl phthalate , Triacetin, ethyl phthalyl ethyl glycolate, trimethyl trimellitate and the like are preferably used. In particular, triphenyl phosphate, biphenyl diphenyl phosphate, diethyl phthalate, ethyl phthalyl ethyl glycolate, and trimethyl trimellitate are preferable.
[0039]
The above plasticizers may be used alone or in combination of two or more. 0.1-20 mass% is preferable with respect to a cellulose acylate, and, as for the addition amount of a plasticizer, 5-15 mass% is more preferable. When the addition amount is less than 0.1% by mass, the effect of addition cannot be sufficiently exhibited, and when the addition amount exceeds 20% by mass, the film surface may bleed out.
[0040]
In addition, in the present invention, (di) pentaerythritol esters described in JP-A No. 11-124445, glycerol esters described in JP-A No. 11-246704, and JP-A No. 2000 are used as plasticizers for reducing the optical anisotropy. Diglycerol esters described in JP-A No.-63560, citric acid esters described in JP-A No. 11-92574, substituted phenyl phosphate esters described in JP-A No. 11-90946 are preferably used.
[0041]
The ultraviolet absorber can be selected from any type according to the purpose, and a salicylic acid ester-based, benzophenone-based, benzotriazole-based, benzoate-based, cyanoacrylate-based, nickel complex-based absorber or the like is used. However, benzophenone series, benzotriazole series, and salicylic acid ester series are preferred. Examples of benzophenone ultraviolet absorbers include 2,4-dihydroxybenzophenone, 2-hydroxy-4-acetoxybenzophenone, 2-hydroxy-4-methoxybenzophenone, 2,2′-di-hydroxy-4-methoxybenzophenone, 2, 2′-di-hydroxy-4,4′-methoxybenzophenone, 2-hydroxy-4-n-octoxybenzophenone, 2-hydroxy-4-dodecyloxybenzophenone, 2-hydroxy-4- (2-hydroxy-3- And methacryloxy) propoxybenzophenone. As a benzotriazole ultraviolet absorber, 2 (2′-hydroxy-3′-tert-butyl-5′-methylphenyl) -5-chlorobenzotriazole, 2 (2′-hydroxy-5′-tert-butylphenyl) ) Benzotriazole, 2 (2′-hydroxy-3 ′, 5′-di-tert-amylphenyl) benzotriazole, 2 (2′-hydroxy-3 ′, 5′-di-tert-butylphenyl) -5 Examples include chlorobenzotriazole, 2 (2′-hydroxy-5′-tert-octylphenyl) benzotriazole, and the like. Examples of salicylic acid esters include phenyl salicylate, p-octylphenyl salicylate, and p-tert-butylphenyl salicylate. Among these exemplified ultraviolet absorbers, in particular, 2-hydroxy-4-methoxybenzophenone, 2,2′-di-hydroxy-4,4′-methoxybenzophenone, 2 (2′-hydroxy-3′-tert-butyl- 5'-methylphenyl) -5-chlorobenzotriazole, 2 (2'-hydroxy-5'-tert-butylphenyl) benzotriazole, 2 (2'-hydroxy-3 ', 5'-di-tert-amylphenyl) ) Benzotriazole, 2 (2′-hydroxy-3 ′, 5′-di-tert-butylphenyl) -5-chlorobenzotriazole is particularly preferred.
[0042]
As the ultraviolet absorber, it is preferable to use a combination of a plurality of absorbers having different absorption wavelengths because a high blocking effect can be obtained in a wide wavelength range. From the viewpoint of preventing deterioration of the liquid crystal, the ultraviolet absorbent for liquid crystal is preferably excellent in the ability to absorb ultraviolet rays having a wavelength of 370 nm or less, and from the viewpoint of liquid crystal display properties, the absorption of visible light having a wavelength of 400 nm or more is small. Examples include oxybenzophenone compounds, benzotriazole compounds, salicylic acid ester compounds, benzophenone compounds, cyanoacrylate compounds, nickel complex compounds, and the like. Particularly preferred ultraviolet absorbers are benzotriazole compounds and benzophenone compounds. Among these, a benzotriazole-based compound is preferable because unnecessary coloring with respect to the cellulose ester is small.
[0043]
As for the ultraviolet absorber, JP-A-60-235852, JP-A-3-199201, JP-A-51907073, JP-A-5-194789, JP-A-5-271471, JP-A-6-107854, JP-A-6-107854, 118233, 6-148430, 7-11056, 7-11055, 7-11056, 8-29619, 8-239509, and JP-A-2000-204173. There is a description.
[0044]
0.001-5 mass% is preferable with respect to a cellulose acylate, and, as for the addition amount of a ultraviolet absorber, 0.01-1 mass% is more preferable. If the addition amount is less than 0.001% by mass, the effect of addition cannot be sufficiently exhibited. If the addition amount exceeds 5% by mass, the ultraviolet absorber may bleed out to the film surface.
[0045]
Further, the ultraviolet absorber may be added at the same time as dissolving the cellulose acylate, or may be added to the polymer solution after dissolution. In particular, a mode in which a UV absorber solution is added to a polymer solution immediately before casting using a static mixer or the like is preferable because spectral absorption characteristics can be easily adjusted.
[0046]
The deterioration inhibitor can prevent cellulose triacetate and the like from deteriorating and decomposing. Examples of the deterioration preventing agent include butylamine, hindered amine compounds (JP-A-8-325537), guanidine compounds (JP-A-5-271471), benzotriazole-based UV absorbers (JP-A-6-235819), and benzophenone-based compounds. There are compounds such as UV absorbers (JP-A-6-118233).
[0047]
Among these, examples of hindered amine compounds include t-butylamine, triphenylamine, and tribenzylamine. Examples of guanidine derivatives include compounds represented by the following formulas (1a) and (2b).
[0048]
[Chemical 1]

[0049]
The addition amount of the deterioration preventing agent is preferably 0.001 to 5%, more preferably 0.01 to 1%. If the addition amount is less than 0.001%, the effect of addition is small, and if the addition amount exceeds 5%, the raw material cost increases, which is disadvantageous.
[0050]
As the fine particle powder, silica, kaolin, talc, diatomaceous earth, quartz, calcium carbonate, barium sulfate, titanium oxide, alumina and the like can be arbitrarily used depending on the purpose. These fine particle powders are preferably dispersed in the binder solution by any means such as a high-speed mixer, a ball mill, an attritor, or an ultrasonic disperser before being added to the polymer solution. As the binder, cellulose acylate is preferable. It is also preferable to carry out dispersion together with other additives such as ultraviolet absorbers. The dispersion solvent is arbitrary, but a composition close to that of the polymer solution solvent is preferable.
[0051]
The number average particle size of the fine particle powder is preferably from 0.01 to 100 μm, particularly preferably from 0.1 to 10 μm. The above dispersion may be added simultaneously to the cellulose acylate dissolving step, or can be added to the polymer solution in any step, but it is preferable to add it just before casting using a static mixer or the like as with the ultraviolet absorber.
[0052]
The content of the fine particle powder is preferably 0.001 to 5% by mass, and more preferably 0.01 to 1% by mass with respect to the cellulose acylate. If the addition amount is less than 0.001% by mass, the effect of addition cannot be exhibited sufficiently, and if the addition amount exceeds 5% by mass, the appearance surface may be deteriorated.
[0053]
As the mold release agent, a surfactant is effective, and is not particularly limited, such as a phosphoric acid type, a sulfonic acid type, a carboxylic acid type, a nonionic type, and a cationic type. These are described in, for example, JP-A-61-243837. 0.001-2 mass% is preferable with respect to a cellulose acylate, and, as for the addition amount of a mold release agent, 0.01-1 mass% is more preferable. If the addition amount is less than 0.001% by mass, the effect of addition cannot be sufficiently exerted, and if the addition amount exceeds 2% by mass, precipitation or insoluble matter may occur.
[0054]
Nonionic surfactants include surfactants having nonionic hydrophilic groups such as polyoxyethylene, polyoxypropylene, polyoxybutylene, polyglycidyl and sorbitan, and specifically include polyoxyethylene alkyl ethers, polyoxyethylene alkyl ethers, and polyoxyethylene alkyl ethers. Oxyethylene alkyl phenyl ether, polyoxyethylene-polyoxypropylene glycol, polyhydric alcohol fatty acid partial ester, polyoxyethylene polyhydric alcohol fatty acid partial ester, polyoxyethylene fatty acid ester, polyglycerin fatty acid ester, fatty acid diethanolamide, triethanolamine Mention may be made of fatty acid partial esters.
[0055]
Examples of the anionic surfactant include carboxylate, sulfate, sulfonate, and phosphate ester salt. Representative examples include fatty acid salt, alkylbenzene sulfonate, alkyl naphthalene sulfonate, alkyl sulfonate, α-olefin sulfonate, dialkylsulfosuccinate, α-sulfonated fatty acid salt, N-methyl-N oleyl taurine, petroleum sulfonate, alkyl sulfate, sulfated oil, polyoxyethylene alkyl ether sulfate, poly Examples thereof include oxyethylene alkyl phenyl ether sulfate, polyoxyethylene styrenated phenyl ether sulfate, alkyl phosphate, polyoxyethylene alkyl ether phosphate, and naphthalene sulfonate formaldehyde condensate.
[0056]
Examples of the cationic surfactant include amine salts, quaternary ammonium salts, pyridinium salts, and the like. Primary to tertiary fatty amine salts, quaternary ammonium salts (tetraalkyl ammonium salts, trialkylbenzyl ammonium salts, Alkyl pyridium salt, alkyl imidazolium salt, etc.). Examples of amphoteric surfactants include carboxybetaine and sulfobetaine, such as N-trialkyl-N-carboxymethylammonium betaine and N-trialkyl-N-sulfoalkyleneammonium betaine.
[0057]
By adding the fluorosurfactant, an antistatic effect can be exhibited. The addition amount of the fluorosurfactant is preferably 0.002 to 2% by mass and more preferably 0.01 to 0.5% by mass with respect to the cellulose acylate. If the addition amount is less than 0.002% by mass, the effect of addition cannot be sufficiently exhibited, and if the addition amount exceeds 2% by mass, precipitation or insoluble matter may occur.
[0058]
In the present invention, a retardation increasing agent (optical property adjusting agent) can be added. The optical anisotropy can be controlled by adding a retardation increasing agent. The retardation increasing agent is preferably an aromatic compound having at least two aromatic rings in order to adjust the retardation of the cellulose acylate film. An aromatic compound is used in 0.01-20 mass parts with respect to 100 mass parts of cellulose acylates. The aromatic compound is preferably used in the range of 0.05 to 15 parts by mass, and more preferably in the range of 0.1 to 10 parts by mass with respect to 100 parts by mass of the cellulose acylate. Two or more aromatic compounds may be used in combination. The aromatic ring of the aromatic compound includes an aromatic hetero ring in addition to the aromatic hydrocarbon ring.
[0059]
The aromatic hydrocarbon ring is particularly preferably a 6-membered ring (that is, a benzene ring). The aromatic heterocycle is generally an unsaturated heterocycle. The aromatic heterocycle is preferably a 5-membered ring, 6-membered ring or 7-membered ring, more preferably a 5-membered ring or 6-membered ring. Aromatic heterocycles generally have the most double bonds. As the hetero atom, a nitrogen atom, an oxygen atom and a sulfur atom are preferable, and a nitrogen atom is particularly preferable. Examples of aromatic heterocycles include furan ring, thiophene ring, pyrrole ring, oxazole ring, isoxazole ring, thiazole ring, isothiazole ring, imidazole ring, pyrazole ring, furazane ring, triazole ring, pyran ring, pyridine ring , Pyridazine ring, pyrimidine ring, pyrazine ring and 1,3,5-triazine ring.
[0060]
In the present invention, a colorant can be added. By adding a colorant, light piping can be prevented when used for a photosensitive material support. The added amount of the colorant is preferably 10 to 1000 ppm, more preferably 50 to 500 ppm in terms of mass ratio with respect to cellulose acylate.
[0061]
In the polymer solution of the present invention, a heat stabilizer such as a salt of an alkaline earth metal such as lucium and magnesium, an antistatic agent, a flame retardant, a lubricant, an oil agent and the like can be appropriately added as necessary. .
[0062]
It describes about the optical characteristic of the film manufactured by the solution casting method of this invention. First, the in-plane retardation (Re) of the film will be described. The measurement method uses an ellipsometer (Ellipsometer AEP-100: manufactured by Shimadzu Corporation), and the in-plane longitudinal and lateral directions at a wavelength of 632.8 nm. Is obtained by multiplying the difference in refractive index by the film thickness.
Re = (nx−ny) × d
nx: refractive index in the horizontal direction
ny: longitudinal refractive index
[0063]
The smaller the retardation (Re) is, the smaller the optical anisotropy in the in-plane direction is, and it is used in the range of 0 to 300 nm depending on the application. The retardation in the thickness direction (Rth) of the film is also important, and is obtained by multiplying the birefringence in the thickness direction at a wavelength of 632.8 nm by the film thickness, and is obtained by the following formula.
Rth = {(nx + ny) / 2−nz} × d
nx: refractive index in the horizontal direction
ny: longitudinal refractive index
nz: refractive index in the thickness direction
[0064]
A smaller refractive index in the thickness direction indicates that there is no optical anisotropy in the thickness direction, but a preferable range is determined depending on the intended use. In general, the Rth of the cellulose acylate film produced according to the present invention is 0 nm to 600 nm per 100 μm, and further used at 0 nm to 400 nm.
[0065]
Films produced by the solution casting method of the present invention can be used as optical films such as polarizing plate protective films, optical compensation sheets, AR, LR, AG film support films, and support films for photographic materials. Can be used.
[0066]
When the film produced by the solution casting method of the present invention is used as an optical compensation sheet, the film itself can be used as the optical compensation sheet. When the film itself is used as an optical compensation sheet, it is preferable to arrange the transmission axis of the polarizing plate and the slow axis of the optical compensation sheet so that they are substantially parallel or perpendicular. The arrangement of the polarizing plate and the optical compensation sheet is described in JP-A-10-48420. The liquid crystal display device comprises a liquid crystal cell having a liquid crystal supported between two electrode substrates, two polarizing plates disposed on both sides thereof, and at least one sheet between the liquid crystal cell and the polarizing plate. An optical compensation sheet is arranged.
[0067]
The liquid crystal layer of the liquid crystal cell is usually formed by sealing liquid crystal in a space formed by sandwiching a spacer between two substrates. The transparent electrode layer is formed on the substrate as a transparent film containing a conductive substance. The liquid crystal cell may further be provided with a gas barrier layer, a hard coat layer, or an undercoat layer (undercoat layer) (used for adhesion of the transparent electrode layer). These layers are usually provided on the substrate. The substrate of the liquid crystal cell generally has a thickness of 50 μm to 2 mm.
[0068]
The optical compensation sheet has birefringence and is used for the purpose of removing the color of the display screen of the liquid crystal display device or improving the viewing angle characteristics. The cellulose acylate film itself according to the present invention can be used as an optical compensation sheet. Further, the function may be imparted as an antireflection layer, an antiglare layer, a λ / 4 layer or a biaxially stretched cellulose acylate film. In addition, in order to improve the viewing angle of the liquid crystal display device, the cellulose acylate film of the present technology and a film exhibiting a birefringence opposite to that (a positive / negative relationship) may be used as an optical compensation sheet. .
[0069]
In addition, optical compensation sheets in which an optically anisotropic layer containing a liquid crystal compound (particularly a discotic liquid crystal molecule) is provided on a support have been proposed (Japanese Patent Laid-Open Nos. 3-9325 and 6-148429). 8-50206 and 9-26572). The film produced by the solution casting method of the present invention can also be used as a support for such an optical compensation sheet.
[0070]
Examples of the polarizing element of the polarizing plate include an iodine polarizing film, a dye polarizing film using a dichroic dye, and a polyene polarizing film. Any polarizing element is generally manufactured using a polyvinyl alcohol film. The protective film of the polarizing plate preferably has a thickness of 25 to 350 μm, and more preferably 40 to 200 μm. The liquid crystal display device may be provided with a surface treatment film. The functions of the surface treatment film include hard coat, anti-fogging treatment, anti-glare treatment and anti-reflection treatment.
[0071]
The optically anisotropic layer is preferably a layer containing negatively uniaxially tilted and aligned discotic liquid crystal molecules. The layer containing the discotic liquid crystalline molecules may be hybrid-aligned in which the angle formed by the disk surface and the support surface changes in the depth direction of the optically anisotropic layer, and the disk surface is parallel to the support surface. Homeotropic alignment, homogeneous alignment in which the disk surface is perpendicular to the support surface, or twist alignment in which the disk surface is twisted in the depth direction of the optically anisotropic layer may be employed. Moreover, the orientation in which these orientations are mixed (for example, hybrid orientation + twist orientation) may be used. Among these, the hybrid orientation is preferable. The optical axis of each discotic liquid crystalline molecule exists in the normal direction of the disk surface. However, the optical axis does not exist in the entire layer in which the discotic liquid crystalline molecules are hybrid-aligned.
[0072]
The film produced by the solution casting method of the present invention can be used for liquid crystal cells in various display modes. TN (Twisted Nematic), IPS (In-Plane Switching), FLC (Ferroelectric Liquid Crystal), AFLC (Anti-Ferroelectric Liquid Nyst) Various display modes such as HAN (Hybrid Aligned Nematic) have been proposed. In addition, a display mode in which the above display mode is oriented and divided has been proposed. The cellulose acylate film is effective in any display mode liquid crystal display device. Further, it is effective in any of a transmissive, reflective, and transflective liquid crystal display device.
[0073]
The film produced by the solution casting method of the present invention may be used as a support for an optical compensation sheet of a TN type liquid crystal display device having a TN mode liquid crystal cell. TN mode liquid crystal cells and TN type liquid crystal display devices have been well known for a long time. The optical compensation sheet used for the TN liquid crystal display device is described in JP-A-3-9325, JP-A-6-148429, JP-A-8-50206, and JP-A-9-26572. Moreover, it is described in Mori et al. (Jpn. J. Appl. Phys. Vol. 36 (1997) p. 143 and Jpn. J. Appl. Phys. Vol. 36 (1997) p. 1068). is there. The TN liquid crystal display device is described in JP-A-10-123478, WO98848320, and Japanese Patent No. 3022477.
[0074]
You may use the film manufactured by the solution casting method of this invention as a support body of the optical compensation sheet | seat of the STN type liquid crystal display device which has a liquid crystal cell of STN mode. In general, in a STN type liquid crystal display device, rod-like liquid crystalline molecules in a liquid crystal cell are twisted in the range of 90 to 360 degrees, and the refractive index anisotropy (Δn) and cell gap (d) of the rod-like liquid crystalline molecules. Product (Δnd) is in the range of 300 to 1500 nm. The optical compensation sheet used in the STN type liquid crystal display device is described in JP-A-2000-105316.
[0075]
The film produced by the solution casting method of the present invention may be used as a support for an optical compensation sheet of a VA liquid crystal display device having a VA mode liquid crystal cell. In the optical compensation sheet used for the VA liquid crystal display device, it is preferable that the direction in which the absolute value of retardation is minimum does not exist in the plane of the optical compensation sheet or in the normal direction. The optical properties of the optical compensation sheet used in the VA liquid crystal display device are determined by the optical properties of the optically anisotropic layer, the optical properties of the support, and the arrangement of the optically anisotropic layer and the support. . When two optical compensation sheets are used in the VA liquid crystal display device, the in-plane retardation of the optical compensation sheet is preferably in the range of −5 nm to 5 nm. Therefore, the absolute value of the in-plane retardation of each of the two optical compensation sheets is preferably 0 to 5. When one optical compensation sheet is used in the VA liquid crystal display device, it is preferable that the in-plane retardation of the optical compensation sheet be in the range of −10 nm to 10 nm.
[0076]
The film produced by the solution casting method of the present invention may be used as a support for an optical compensation sheet of an OCB type liquid crystal display device having an OCB mode liquid crystal cell or a HAN type liquid crystal display device having a HAN mode liquid crystal cell. Good. In the optical compensation sheet used for the OCB type liquid crystal display device or the HAN type liquid crystal display device, it is preferable that the direction in which the absolute value of retardation is minimum does not exist in the plane of the optical compensation sheet or in the normal direction. The optical properties of the optical compensation sheet used in the OCB type liquid crystal display device or the HAN type liquid crystal display device are also the optical properties of the optically anisotropic layer, the optical properties of the support, and the optically anisotropic layer and the support. Is determined by the arrangement of An optical compensation sheet used for an OCB type liquid crystal display device or a HAN type liquid crystal display device is described in JP-A-9-197397. Moreover, it is described in Mori et al. (Jpn. J. Appl. Phys. Vol. 38 (1999) p. 2837).
[0077]
The film produced by the solution casting method of the present invention may be used as a support for an optical compensation sheet of an ASM type liquid crystal display device having a liquid crystal cell of ASM (Axial Symmetrical Microcell) mode. The ASM mode liquid crystal cell is characterized in that the thickness of the cell is maintained by a resin spacer whose position can be adjusted. Other properties are the same as those of the TN mode liquid crystal cell. The ASM mode liquid crystal cell and the ASM type liquid crystal display device are described in a paper (Kume et al., SID 98 Digest 1089 (1998)) outside Kume.
[0078]
【Example】
In the solution casting process, the raw materials used are as follows.
100 parts by weight of cellulose triacetate
10 parts by weight of triphenyl phosphate
5 parts by weight of biphenyl diphenyl phosphate
315 parts by weight of methylene chloride
60 parts by weight of methanol
10 parts by weight of n-butanol
[0079]
Side stream polymer solution composition during co-casting
100 parts by weight of cellulose triacetate
10 parts by weight of triphenyl phosphate
5 parts by weight of biphenyl diphenyl phosphate
400 parts by weight of methylene chloride
75 parts by weight of methanol
n-Butanol 13 parts by weight
The presence or absence of air entrainment and the stability of the casting ribbon were observed under each condition in the examples.
[0080]
[Example 1]
Film formation was performed under the following conditions.
1) Distance h = 3 mm between casting die and support
2) Casting speed v = 45m / min
3) Base thickness t = 80 μm
4) Back suction static pressure p = -30 Pa
5) Distance d = 1.0 mm between back suction device and casting band
Air entrainment did not occur, and the casting ribbon was stable.
[0081]
[Example 2]
Film formation was performed by the co-casting method under the following conditions.
1) Distance h = 3 mm between casting die and support
2) Casting speed v = 45m / min
3) Base thickness t = 80 μm, mainstream thickness = 76 μm, sidestream thickness (upper and lower layers) = each 2 μm
4) Back suction static pressure p = -30 Pa
5) Distance d = 1.0 mm between back suction device and casting band
Air entrainment did not occur, and the casting ribbon was stable.
[0082]
[Example 3]
Film formation was carried out under the following conditions by changing the polymer solution formulation.
100 parts by weight of cellulose triacetate
10 parts by weight of triphenyl phosphate
5 parts by weight of biphenyl diphenyl phosphate
315 parts by weight of methyl acetate
60 parts by weight of ethanol
10 parts by weight of n-butanol
[0083]
Cellulose triacetate was swollen with a solvent for 30 minutes, cooled at -70 ° C, and heated to 50 ° C and dissolved.
1) Distance h = 3 mm between casting die and support
2) Casting speed v = 45m / min
3) Base thickness t = 80 μm
4) Back suction static pressure p = -30 Pa
5) Distance d = 1.0 mm between back suction device and casting band
Air entrainment did not occur, and the casting ribbon was stable.
[0084]
[Comparative Example 1]
Film formation was performed under the following conditions.
1) Distance h = 3 mm between casting die and support
2) Casting speed v = 45m / min
3) Base thickness t = 80 μm
4) No back suction
Air companion occurred and it was impossible to continue casting.
[0085]
[Comparative Example 2]
Film formation was performed under the following conditions.
1) Distance h = 3 mm between casting die and support
2) Casting speed v = 45m / min
3) Base thickness t = 80 μm
4) Back suction static pressure p = -2 Pa
5) Distance d = 1.0 mm between back suction device and casting band
Air companion occurred and it was impossible to continue casting.
[0086]
[Comparative Example 3]
Film formation was performed under the following conditions.
1) Distance h = 3 mm between casting die and support
2) Casting speed v = 45m / min
3) Base thickness t = 80 μm
4) Back suction static pressure p = -30 Pa
5) Distance d = 3.5 mm between back suction device and casting band
Air entrainment did not occur, but the casting ribbon shook and was not stable.
[0087]
[Durability evaluation of polarizing plate]
A polarizing plate was prepared using the film formed by the method of Examples 1 to 3 as a polarizing plate protective film, and the durability was evaluated.
[0088]
<Method for creating polarizing plate>
A polarizing plate sample was prepared by bonding polyvinyl alcohol adhesive on both surfaces of a polarizing element on which iodine was adsorbed by stretching polyvinyl alcohol. This polarizing plate sample was exposed for 500 hours in an atmosphere of 60 ° C. and 90% RH. In any case, the degree of polarization was 99.6% or more, and sufficient durability was recognized.
[0089]
<Evaluation method of polarization degree>
The parallel transmittance Yp and the orthogonal transmittance Yc in the visible region are obtained by a spectrophotometer, and the polarization degree P is determined based on the following equation.
P = √ ((Yp−Yc) / (Yp + Yc))
[0090]
[Example 4]
<Preparation of cellulose triacetate solution>
Cellulose triacetate powder (average size: 2 mm) was gradually added and charged into a stainless steel dissolution tank having stirring blades while thoroughly stirring the following solvent mixed solution. After the addition, the mixture was allowed to stand at room temperature (25 ° C.) for 3 hours at 25 ° C. to swell the cellulose triacetate. In addition, methyl acetate, cyclopentanone, acetone, methanol, and ethanol, which are solvents, all have a water content of 0.2% by mass or less.
[0091]
16 parts by weight of cellulose triacetate
(Substitution degree 2.83, viscosity average polymerization degree 320, water content 0.4 mass%, viscosity 305 mPa · s of 6 mass% in methylene chloride solution)
53 parts by mass of methyl acetate
10 parts by mass of cyclopentane
5 parts by mass of acetone
5 parts by mass of methanol
5 parts by mass of ethanol
3 parts by mass of plasticizer A (dipentaerythritol hexaacetate)
3 parts by mass of plasticizer B (triphenyl phosphate)
Fine particle powder (silica (particle size 20 nm)) 0.1 parts by mass
UV absorber a 0.1 mass part
(2,4-Bis- (n-octylthio) -6- (4-hydroxy-3,5-di-tert-butylanilino) -1,3,5-triazine)
UV absorber b 0.1 parts by mass
(2 (2′-hydroxy-3 ′, 5′-di-tert-butylphenyl) -5-chlorobenzotriazole)
UV absorber c 0.1 parts by mass
(2 (2′-Hydroxy-3 ′, 5′-di-tert-amylphenyl) -5-chlorobenzotriazole
C ₁₂ H _{twenty five} OCH ₂ CH ₂ O-P (= O)-(OK) ₂ 0.05 parts by mass
[0092]
The viscosity of this solution obtained by the cooling dissolution method described later was 160 Pa · S (45 ° C.).
[0093]
<Cooling dissolution of cellulose triacetate solution>
The cellulose triacetate solution described above was fed by a screw extruder and passed through the cooling part at −70 ° C. for 3 minutes. Cooling was performed using a refrigerant at −80 ° C. (3M, “Fluorinert”) cooled by a refrigerator. The solution obtained by cooling is heated to 120 ° C. by a heat exchanger provided with a static mixer, held for 3 minutes, cooled, transferred to a stainless steel container at 50 ° C., and heated at 50 ° C. The mixture was stirred for 2 hours for defoaming. The cellulose triacetate solution thus prepared was filtered with a filter paper having an absolute filtration accuracy of 0.01 mm (manufactured by Toyo Filter Paper Co., Ltd., “# 63”), and further a filter paper having an absolute filtration accuracy of 0.0025 mm (manufactured by Pall, (FH 025)).
[0094]
<Production of cellulose triacetate film>
The cellulose triacetate solution obtained by the above-described dissolution method was brought to 50 ° C. and cast on a mirror-surface stainless steel casting support through a casting Gieser. For drying, 120 ° C. drying air was blown. After 2 minutes, the film was peeled off from the mirror stainless steel casting support, and then dried at 110 ° C. for 10 minutes and further at 150 ° C. for 30 minutes to obtain a cellulose triacetate film (film thickness 40 μm).
[0095]
Film formation was performed under the following conditions.
1) Distance h = 2mm between casting die and support
2) Casting speed v = 40m / min
3) Base thickness t = 40 μm
4) Back suction static pressure p = -100 Pa
5) Distance d = 0.5mm between back suction device and casting band
6) Application width = 100cm
7) Casting support temperature = 10 ° C.
Air entrainment did not occur, and the casting ribbon was stable.
[0096]
<Preparation of polarizing plate a>
A polarizing element is prepared by adsorbing iodine to a stretched polyvinyl alcohol film, and the cellulose triacetate film is placed on both sides so that its slow axis is parallel to the transmission axis of the polarizing element using a polyvinyl alcohol-based adhesive. Pasted.
[0097]
The polarizing plate a was exposed for 500 hours in an atmosphere of 80 ° C. and 90 RH, and the degree of polarization was measured by the method described above. The degree of polarization was 99.6% or more, and sufficient durability was recognized.
[0098]
<Preparation of polarizing plate b>
A polarizing element is prepared by adsorbing iodine to a stretched polyvinyl alcohol film, and using the polyvinyl alcohol adhesive, the cellulose triacetate film is placed on one side so that its slow axis is parallel to the transmission axis of the polarizing film. At the same time, the cellulose triacetate film was saponified, and attached to the opposite side of the polarizing film using a polyvinyl alcohol-based adhesive. Furthermore, an optical compensation sheet (manufactured by Fuji Photo Film Co., Ltd., “WV film”) is attached to the cellulose triacetate film side using an adhesive so that its slow axes are parallel to each other, and an optical compensation sheet is attached. A combined polarizing plate was prepared.
[0099]
This polarizing plate b was exposed for 500 hours in an atmosphere of 80 ° C. and 90 RH, and the degree of polarization was measured by the method described above. The degree of polarization was 99.6% or more, and sufficient durability was recognized.
[0100]
<Evaluation with liquid crystal display>
The polarizing plate a and the polarizing plate b were mounted on a TFT (Thin Film Transistor) type liquid crystal display device. As a result, a good viewing angle and contrast could be obtained.
[0101]
[Example 5]
<Preparation of cellulose triacetate solution for inner layer>
Cellulose triacetate powder (average size 2 mm) was gradually added to a stainless steel dissolution tank having stirring blades while stirring well in the following solvent mixed solution. After the addition, the mixture was left at room temperature (25 ° C.) for 3 hours to swell the cellulose triacetate. The solvents methyl acetate, cyclopentanone, acetone, methanol, and ethanol were all used with a water content of 0.2% by mass or less.
[0102]
16 parts by weight of cellulose triacetate
(Substitution degree 2.83, viscosity average polymerization degree 320, water content 0.4 mass%, viscosity 305 mPa · s of 6 mass% in methylene chloride solution)
53 parts by mass of methyl acetate
10 parts by mass of cyclopentane
5 parts by mass of acetone
5 parts by mass of methanol
5 parts by mass of ethanol
3 parts by mass of plasticizer A (dipentaerythritol hexaacetate)
3 parts by mass of plasticizer B (triphenyl phosphate)
Fine particle powder (silica (particle size 20 nm)) 0.1 parts by mass
UV absorber a 0.1 mass part
(2,4-Bis- (n-octylthio) -6- (4-hydroxy-3,5-di-tert-butylanilino) -1,3,5-triazine)
UV absorber b 0.1 parts by mass
(2 (2′-hydroxy-3 ′, 5′-di-tert-butylphenyl) -5-chlorobenzotriazole)
UV absorber c 0.1 parts by mass
(2 (2′-Hydroxy-3 ′, 5′-di-tert-amylphenyl) -5-chlorobenzotriazole
C ₁₂ H _{twenty five} OCH ₂ CH ₂ O-P (= O)-(OK) ₂ 0.05 parts by mass
[0103]
The viscosity of this solution obtained by the cooling dissolution method was 60 Pa · S (45 ° C.).
[0104]
<Cooling dissolution of cellulose triacetate solution for inner layer>
The cellulose triacetate solution described above was fed with a screw extruder and passed through the cooling part at -70 ° C for 3 minutes. Cooling was performed using a -80 ° C refrigerant (3M, "Fluorinert") cooled by a refrigerator. The solution obtained by cooling is heated to 120 ° C. by a heat exchanger provided with a static mixer, held for 3 minutes, cooled, transferred to a stainless steel container at 50 ° C., and heated at 50 ° C. The mixture was stirred for 2 hours for defoaming. The cellulose triacetate solution is filtered with a filter paper having an absolute filtration accuracy of 0.01 mm (“Toyo Filter Paper Co., Ltd.,“ # 63 ”), and further filtered with an absolute filtration accuracy of 0.0025 mm (“ FH 025 ”, manufactured by Paul). Filtered through.
[0105]
<Preparation of cellulose triacetate solution for outer layer>
The above-described inner layer cellulose triacetate solution was charged in the same manner except that cellulose triacetate was changed to 19 parts by mass and methyl acetate was changed to 44 parts by mass. The viscosity of this solution obtained by the cooling dissolution method was 25 Pa · S (45 ° C.).
[0106]
<Cooling dissolution of cellulose triacetate solution for outer layer>
The cellulose triacetate solution described above was fed with a screw extruder and passed through the cooling part at -70 ° C for 3 minutes. Cooling was performed using a -80 ° C refrigerant (3M, "Fluorinert") cooled by a refrigerator. The solution obtained by cooling is heated to 120 ° C. by a heat exchanger provided with a static mixer, held for 3 minutes, cooled, transferred to a stainless steel container at 50 ° C., and heated at 50 ° C. The mixture was stirred for 2 hours for degassing. The cellulose triacetate solution is filtered with a filter paper having an absolute filtration accuracy of 0.01 mm (“Toyo Filter Paper Co., Ltd.,“ # 63 ”), and further filtered with an absolute filtration accuracy of 0.0025 mm (“ FH 025 ”, manufactured by Paul). Filtered through.
[0107]
<Production of cellulose triacetate film>
Place the above-mentioned cellulose triacetate solution on a casting support that is made of metal using a three-layer co-casting die, with the cellulose triacetate solution for the inner layer on the inside and the cellulose triacetate solution for the outer layer on both sides. After discharging and multilayer casting, the casting membrane is peeled off from the casting support and dried to form a three-layer cellulose triacetate film laminate (inner layer thickness: 80 μm, each surface layer thickness: 2 μm) Was made.
[0108]
Film formation was performed under the following conditions.
1) Distance h = 5 mm between casting die and support
2) Casting speed v = 50m / min
3) Base thickness t = 84 μm
4) Back suction static pressure p = -50 Pa
5) Distance d = 1.0 mm between back suction device and casting band
6) Application width = 100cm
7) Casting support temperature = 10 ° C.
Air entrainment did not occur, and the casting ribbon was stable.
[0109]
The film peeled off from the casting support is dried while being conveyed by a tenter, dried at 100 ° C. for 3 minutes and 130 ° C. for 5 minutes, and then dried stepwise at 150 ° C. for 10 minutes to evaporate the solvent. To obtain a cellulose triacetate film.
[0110]
<Preparation of polarizing plate c>
A polarizing element is prepared by adsorbing iodine to a stretched polyvinyl alcohol film, and the cellulose triacetate film is placed on both sides so that its slow axis is parallel to the transmission axis of the polarizing element using a polyvinyl alcohol-based adhesive. Pasted. This polarizing plate c was exposed for 500 hours in an atmosphere of 80 ° C. and 90 RH, and the degree of polarization was measured by the method described above. The degree of polarization was 99.6% or more, and sufficient durability was recognized.
[0111]
<Preparation of polarizing plate d>
A polarizing element is prepared by adsorbing iodine to a stretched polyvinyl alcohol film, and using the polyvinyl alcohol adhesive, the cellulose triacetate film is placed on one side so that its slow axis is parallel to the transmission axis of the polarizing element. At the same time, the cellulose triacetate film was saponified, and attached to the opposite side of the polarizing element using a polyvinyl alcohol-based adhesive. Furthermore, an optical compensation sheet (manufactured by Fuji Photo Film Co., Ltd., “WV film”) is attached to the cellulose triacetate film side using an adhesive so that its slow axes are parallel to each other, and an optical compensation sheet is attached. A combined polarizing plate was prepared.
[0112]
This polarizing plate d was exposed for 500 hours in an atmosphere of 80 ° C. and 90 RH, and the degree of polarization was measured by the method described above. The degree of polarization was 99.6% or more, and sufficient durability was recognized.
[0113]
<Evaluation with liquid crystal display>
The polarizing plate c and the polarizing plate d were mounted on a TFT (Thin Film Transistor) type liquid crystal display device. As a result, a good viewing angle and contrast could be obtained.
[0114]
【The invention's effect】
According to the present invention, production efficiency for producing a cellulose acetate film using a casting band can be improved.
[Brief description of the drawings]
FIG. 1 is a schematic view of a casting die part of a solution casting apparatus.
FIG. 2 is a schematic view of a solution casting apparatus for performing the solution casting method of the present invention.
FIG. 3 is a plan view of a casting die part of FIG. 1;
FIG. 4 is a bottom view of the same back suction device.
FIG. 5 is a schematic cross-sectional view of a casting die used in a solution casting apparatus for performing the solution casting method of the present invention.
FIG. 6 is a schematic cross-sectional view of a casting die used in a solution casting apparatus for performing the solution casting method of the present invention.
FIG. 7 is a schematic cross-sectional view of a casting die used in a solution casting apparatus for performing the solution casting method of the present invention.
[Explanation of symbols]
1 ... Ribbon polymer solution
2 ... Support
3 ... decompression chamber
4 ... Ribbon
10 ... Casting die
11 ... Manifold
12 ... Manifold
13 ... Manifold
14 ... Feed block
20 ... Rotating drum
21 ... Stripping roller
30 ... Casting band (support)
40. Back suction device
41 ... decompression chamber
42 ... decompression chamber
43 ... Suction duct connection port
44 ... partition
45 ... Labyrinth
50 ... Suction duct
60 ... Buffer tank
70 ... Blower
80 ... Casting drum

Claims (12)

  In the solution casting method using a casting band, a back suction device is provided behind the casting die, the distance between the back suction device and the casting band is 0.3 to 3 mm, and the back suction device is A front decompression chamber disposed on the downstream side, a rear decompression chamber disposed on the upstream side, and a suction duct connected near both side ends of the upper surface of the rear decompression chamber. A method for forming a cellulose acetate solution, wherein the vacuum chamber and the vacuum chamber on the rear side are partitioned by a partition and communicate with each other only by a gap between the casting band and the casting band.   The solution casting method according to claim 1, wherein the static pressure of the back suction is set to -10 Pa to -500 Pa.   3. The solution casting method according to claim 2, wherein the end portion in the width direction of the back suction device has a labyrinth structure.   4. The solution casting method according to claim 2, wherein a width of the back suction device is wider than the casting ribbon width, and suction is also performed from the outside of the end portion of the casting ribbon. Characterized in that the material gap does not damage the back suction device belt of rubber surface of the narrowest portion of the back suction device and the belt, according to claim 2, 3 or 4 solution made according Membrane method   The polymer solution cast from the casting die to the casting band is a cellulose acylate solution, and the solvent is composed of methyl acetate, ketones and alcohols, and the solvent ratio is 20 to 90% by mass of methyl acetate, The solution casting method according to claim 1, 2, 3, 4, or 5, wherein the ketone is 5 to 60% by mass and the alcohol is 5 to 30% by mass.   The polymer solution cast from the casting die to the casting band is a cellulose acylate solution, and contains at least one plasticizer in an amount of 0.1 to 20% by mass with respect to the cellulose acylate. The solution casting method according to 2, 3, 4, 5 or 6.   The polymer solution cast from the casting die to the casting band is a cellulose acylate solution, and contains at least one ultraviolet absorber in an amount of 0.001 to 5 mass% with respect to the cellulose acylate. The solution casting method according to 1, 2, 3, 4, 5, 6 or 7.   The polymer solution cast from the casting die to the casting band is a cellulose acylate solution, and contains at least one kind of fine particle powder in an amount of 0.001 to 5% by mass with respect to the cellulose acylate. The solution casting method according to 1, 2, 3, 4, 5, 6, 7 or 8.   The polymer solution cast from the casting die to the casting band is a cellulose acylate solution, and contains at least one release agent in an amount of 0.001 to 2% by mass with respect to the cellulose acylate. The solution casting method according to 1, 2, 3, 4, 5, 6, 7, 8, or 9.   The polymer solution cast from the casting die to the casting band is a cellulose acylate solution, and contains at least one fluorine-based surfactant in an amount of 0.002 to 2% by mass with respect to the cellulose acylate. The solution casting method according to claim 1, 2, 3, 4, 5, 6, 7, 8, 9 or 10.   The polymer solution comprising two or more types of cellulose acylate solutions is co-cast when the polymer solution is cast from the casting die to the casting band. The solution casting method according to 8, 9, 10 or 11.

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